Method of making a phenolic resin metal containing molding composition



Patented Nov. 15, 1949 METHOD OF MAKING A PHENOLIC RESIN METAL CONTAINING MOLDING COMPO- SITION William P. Roush, Pittsburgh, Pa.

No Drawing. Application January 31, 1947, Serial No. 725,731

3 Claims.

This invention relates .to synthetic resins such as are commonly termed plastics, and more particularly to composite plastics consisting of resin and metal particles having decorative, electrical and mechanical properties adapted to a variety of uses.

It is well known in the art that synthetic resins such as the well known phenolic condensation products may be compounded with fillers, such as wood flour, paper, fabrics and the like, such fillers constituting the body of the finished product in which the resin is the binder that becomes iniusible upon solidification in its final molding operation.

In accordance with the present invention the molding composition contains metal particles and resinous materials, such, for example, as aluminum powder or flake, also bronzing powdersand copper, iron or other highly conducting metals in flake or powder form to form molded articles of highly decorative surface finishes and 01- desirable physical or electrical properties. The invention distinguishes from the prior art mainly in that the composite metal and resinous product is combined in the preparation of the molding composition per se, and is not merely added or suspended as in conventional practice.

For example, a typical molding composition embodying the principles of this invention may consist of 103 parts of phenol and 14 parts of hexamethylenetetramine heated together at 130 C., the reaction being exothermic, and increasing the temperature to about 180 C. During the reaction ammonia is evolved and when it ceases to come ofi the reaction product is again heated at 185 C. for four hours for driving ofi most of the nitrogen. The resultant resin is permanently fusible and is used as the base stock for the preparation of the composite metal resin compound.

To the base thus formed held at a temperature of 150 C. there is added 12 parts of aluminum powder, the powder being added slowly with good agitation. Thus the ratio is ten parts of resin to one part of metal powder which may be varied in accordance with the color of the resin, whether light or dark.

The mixture is cooled to 105 C. and 15 parts of formaldehyde in the form of a 40% solution, and /2 Part of 'hexamethylenetetramine are added. Also 3 parts of aluminum stearate are added as a lubricating agent. The mixture is held at 105 C. for approximately two hours or as long as the material is viscous with strong agitation to eliminate all water present. It is then cooled and held at 70 C. until hardening takes place. The hard material is cooled completely and is broken up and finely ground to constitute the finished molding compound which is in an advanced stage of infusibility. The molding composition will not actually melt at any temperature, but above C. it will soften suificiently to flow properly in a mold at a temperature of approximately C., the molding step embodying generally the same technique as with conventional phenolic molding preparations.

Articles made of this composition when of thin cross section will harden in one or two minutes and the finished product may be ejected from the mold without cooling. The metal particles of the composition appear on the surface of the finished product, lending to it the appearance of a highly polished metal article. It thus distinguishes from the use of compositions employing fillers in which such fillers do not appear on the surface of the finished article and in which considerable care is exercised to prevent the filler from showing on the surface and marring the finish. In the composition of the present invention the metal particles produce the desired surface appearance and the resins cement the particles together and give the object the necessary strength.

The only limit on the ratio of metal to resin is therefore enough metal to overcome the color of the resin and produce the desired metallic finish. With a light colored resin as little as one part metal to 25 parts of resin has been found to be sufiicient as distinguished from the ten to one ratio of the above example. By using a light colored resin dyed to a brilliant color and a small amount of metal powder, such as one part of metal powder with 50 parts by weight of resin, the resultant product when molded will have a highly lustrous metallic finish with a colored sheen and an appearance of depth.

By using a molding composition of resin and electrical conducting metal powders, such as copper, aluminum, iron and th like, it is possible to "produce articles possessing valuable electrical properties. By carefully controlling the proportion of metal to resin it is possible to produce objects of definite desired conductivity. Each particle of metal is enveloped in a film of resin which is not a perfect electrical insulator and is capable Of transmitting a certain amount of current. The higher the proportion of metal powder in the composition the closer the metal particles are packed and the thinner will be the resinous film therebetween, so that the finished article will have greater current conductivity. An electrical application for such products would be an inexpensive rheostat or resistor. Another is the fabrication of electric condensers. Ordinary phenolic condensation products are well known for their dielectric properties and are well adapted for such application.

Another application is the fabrication of noninductive resistors for high frequency work. lhe low loss polystyrenes are; well known for their dielectrio'streng'th in this field and may be used as a resinous binder for the metallic resin com-..

position. Also for use of the material in electrical application the proportionof metal to. resin is far greater than in composite structures for ornamental surface decorative uses. For example, in electrical application about one-parting: metal powder or fiake is used to two parts of same, and then breaking and grinding th h d- .11% IQQmDQ tiQ H QII he desired mesh size of a "mflliiingzmixture.

stock consisting of 103 parts. of phenol and 14 resin, or about five parts of metal to 'oneipa rc f .aapartsl of;ahexamethylenetetramme heated toresin may be used, depending upon the electrical conditions of the application and the size and shape of the article. With the larger proportions oi rmetal to resin care must be exercised to coat ea c tal particle with the resin to provide the necessary inecha'nical strength.

:Becauseoithe physical and mechanical properties f-the composite metal resinous products described "above; they may be utilized as gears, pulleys, couplings, etc.',' they being heat resistant and superior surface abrasion resistance. Articles rriay be machined from a suitable precast i i dbank.

Another advantage of the composite metal resin materials is'that they cure faster due to the greater conductivity of the metal comp und dmate i It is evident'from the foregoing description of thefinvention that composite metal resinous bodies having a metallic appearance may" be formed" by initially preparing a base stock in fusible state and adding metallic powder or flake. Compositionswith small metal content require no special technique for blending with the resin. For larger metal contents it is best to add the metal to moiten resin during preparation to 'insure thateach metal particle is completely coated so as to give to thefinal product the chemical I properties 'ofthe resin with which the metal particles are compounded. The composite metal [and resinmolding compositions may also be blended by precipitating resin onto the metal particles from solutionflor. kneading on hot rolls or in afDanbury mixer.

f The composition of metal and resin can be varied in' proportion and substance to produce desired surface. finish or electrical, physical and mechanical properties adapting it to a variety, of 'uses.- Also-two or more tone effects are pos sible' through use of different metals, such as aluminum powder and resin composition inlaid on a bronze powder and resin composition.

Although, several embodiments of the invention have been illustrated and described, it will be evident to those skilled in the art that various modifications'may be made in the details of con struction without departing from the principles herein set forth. I-claim: 1. "I hemethod of making a molding composition which comprises heating 103 parts of phenol and '14 parts of hexamethylenetetramine atj130? C. until ammonia ceases to come off, reheating:

4 the reaction product at 185 C. for approximately four hours to drive off most of the nitrogen, reducing the temperature of the above base resin to 150 C., slowly adding from 5 to 12 parts of metal particles with good agitation, cooling the mixture to C., adding 15 parts of a forty per cent solution of formaldehyde, part hexamethylenetetramine and 3 parts aluminum stearatelstrongly agitating the mixture to remove all water, cooling the mixture to 70 C. to harden the 2. The methodofmaking a molding composition. which, comprises initially preparing a base :;Tg'ether at 130 C. until ammonia ceases to come .off, reheating the reaction product at 185 C. for

approximately four hours to drive ofi most of he n rsz s aving, he e u tan resin Permanently fusible, reducing the temperature of the wer siq thus brni lji 0ic gsl wl asislin w th. o agitation. m ta Par cl wder.

mrva e he o qh'qfi i i altwder to'the resin in accordance with-the color of: the esi Pr d a i ed. e all finism tm rqrd io o metal. e n e s hht q' re resins, cooling the migture to l05 i 0.; adding -15 parts a 9 e t s lutionqfi tmaldhrsieti /2 a am i ene ei amine and. um nu t ar t tron ly-a i atin he" 3 tur remove 1 Water eqdlipg' hei ixture to '70 C. to harden the same, and'then-brealging g n in he. har ened composition; to t si ed me zeoi amoldine'mixiura 1 e hod at mak ng. a melding .QQmrnsiAQ tion which comprises initially J preparing a b;ase

Stock c nsi t n '9 p s 92' h nol and; 4. pa X meth en te ram ne heated togeth r? until Q 51 0.CQI $..-Qfi,-re

e t ng t e ea tion, prec n at 859] c. recap; prqx mat y fo r. ou s I a-drive .ofi. 1 1 9 of, the nitrogen, eavin l ei s lta i res nrermane y fusible. reducin the..temp,erature ..or .tliejwbgise; stock thus iormedto1150. C., slowly adding' with good agitation .metal art des, nfl termjvam ing the proportion of themetal' powdertofthe resin in. accord n wi the. color .of'the to produce, a des ed metalliciinishgthe,p

tion 0; metal being less, with light colored re pq in the m s rew o 105 .c..'.a i i1 -15 lpar s oi a 40 percent solutionoi, iormaldehyde, part exa ii thylenet iramine and- 3 r al m nu 7 tearat .stroi gl as iat ng the mi ure .to. Ire?! move all water, cooling the mixtureto 70250;.

t harden he. same. and thenf-breaking a inq nst ell rdened. composition. to; e new h zepf amo sii g'm tu e. 1 WILLIAM -P..BOII$I-l-.

EFEBEKQEQCIZCED. The follow'ng references are oi record. inithe file of thispatent:

'UNITED STATES'PATENTS;

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